1. Field of the Invention
The present invention relates to a semiconductor device, a manufacturing method thereof, and an electronic device including the semiconductor device.
2. Description of the Related Art
A thin film transistor (TFT) is a transistor formed using a semiconductor. In recent years, in order to improve performance of a semiconductor device, various technologies have been examined in accordance with increasing in integration degree of thin film transistors and downsizing of semiconductor devices using a thin film transistor.
With downsizing of semiconductor devices, parasitic resistance between a source region and a drain region of a thin film transistor cannot be ignored, and sheet resistance is increased.
When the sheet resistance of the source region and the drain region is increased, a problem arises in that current drive capability is deteriorated in a semiconductor device which is manufactured.
In order to solve the forgoing problem, with respect to a thin film transistor, a technique has been developed in which a high-concentration impurity layer is stacked over a semiconductor layer and only the high-concentration impurity layer is etched not to promote etching of a lower semiconductor layer using difference in etching rate between the two layers in dry etching (Non-Patent Document 1: “Raised source and drain structure of poly-Si TFTs” Electrochemical Society Proceeding).
By using this technique, a thin film transistor in which resistance of a source region and a drain region is lowered can be manufactured using a stacked portion of a semiconductor layer and a high-concentration impurity layer for the source region and the drain region.